Corrosion in industrial water systems is a serious problem. It causes undesirable consequences, including loss of heat transfer, increased cleaning frequency, equipment repairs and replacements, shutdowns, environmental problems and the increasing resources and costs associated with each.
Treatment of corrosion in water systems is typically achieved by continuous application of various corrosion inhibitors in the water including, for example, phosphates, polymer, chromates, zinc, molybdates, nitrites, and combinations thereof. These inhibitors work by the principle of shifting the electrochemical corrosion potential of the corroding metal in the positive direction indicating the retardation of the anodic process (anodic control), or displacement in the negative direction indicating mainly retardation of the cathodic process (cathodic control). Corrosion inhibitors act on the cathode and/or anode of the corrosion cell.
Historically, the use of Tin compounds as a corrosion inhibitor has been the subject of some experimentation in industrial water systems. Stannous salts are known to inhibit corrosion but, unlike more conventional corrosion inhibitors, the mechanism by which the stannous salts inhibited corrosion was not well understood. Previous corrosion inhibition programs utilized the stannous salts in much the same manner as conventional corrosion inhibitors in which doses of the stannous inhibitors were introduced into the aqueous systems to maintain a minimum stannous concentration in order to be effective. Examples of such methods may be found in, for example, U.S. Pat. No. 7,910,024 to Stapp et al. and U.S. Pat. Nos. 6,001,156 and 6,200,529 to Riggs, Jr., the contents of which are incorporated herein by reference, in their entireties.
Moreover, conventional corrosion inhibition practices with Tin compounds have not been able to effectively deal with the problem of maintaining an effective amount of Tin(II) in solution long enough to form a protective film on the surface of the corrosive metal without losing the active form, Tin (II), perhaps due to bulk phase oxidation and precipitation to Tin (IV). Further, use of organic compounds as corrosion inhibitors has been challenging and, in many cases, prohibitive due to volume and cost requirements. These and other issues are addressed by the present disclosure.